Stackable risers, such as disclosed in U.S. Pat. Nos. 5,617,679 and 5,852,901, assigned to Tuf-Tite, Inc., the assignee of the present disclosure, provide modular solutions to gaining access from at or near grade level to underground septic tanks and other underground on-site waste and drainage units. Another stackable riser component, known as a riser pan, was disclosed in co-pending U.S. patent application Ser. No. 10/352,086, Publication No. US 2003/0145527 A1, also assigned to Tuf-Tite, Inc. In order for the stackable risers and riser pans to be used with access opening(s) of concrete septic tanks or other concrete on-site waste units, it was typical to cast a lowermost riser or riser pan into the concrete lid of the tank.
As used herein, the term “concrete lid” of the septic tank refers to the large, horizontally-oriented concrete slab, typically on the order of 4 feet by 8 feet and several inches thick, for example, provided at the top of the septic tank (having a typical capacity from about 750 to about 1,250 gallons, with some septic tanks having a capacity of about 1,500 gallons or more), and supported by the walls of the septic tank. The term “concrete cover”, as used herein, refers to the well-known removable, generally smaller (and typically round) cover member associated with an opening in the concrete lid and used to gain access to the interior of the septic tank. Such concrete covers are generally flat, have cylindrically-shaped outer peripheral walls, while others may have tapered walls, or may include a stepped wall portion. The concrete covers sit atop the concrete lid, over the lid's access opening, or in a frustro-conical portion of a riser pan. These concrete covers allow a point of access to the interior of the septic tanks for purposes of inspection, drainage, cleaning, or other maintenance, including access to effluent filters provided at the inlet or outlet of the septic tank, such as for cleaning or replacement of the filters.
Septic tanks and other underground on-site waste or drainage facilities need not be made of concrete. For example, plastic septic tanks, such as formed of polyethylene, having a capacity of about 1,000 to about 1,500 gallons, are increasingly prevalent. Smaller plastic underground structures, with a capacity of about 300 to about 500 gallons, are also available, and are used, for example, as so-called pump stations or lift stations.
Access to the interior of all these various concrete or plastic structures is necessary from time to time for maintenance, repairs, cleaning, filter replacement, and the like. Manholes or similar access means have been provided in these structures to provide such interior access. However, since the access means for these structures are often buried at least several inches, and more often several feet, below grade level, it is desirable to provide an access column of one or more risers, whether formed of concrete or plastic, above the access means to avoid having to dig down to reach the access means.
A column of risers is preferably capped by a riser cover. It is conventional for a column of plastic risers to be capped by a plastic riser cover. By providing a riser pan within the column at some point therealong, it is possible for a secondary cover, such as a concrete cover, to be provided within a column of risers. Alternatives to risers include corrugated polyethylene pipe and ribbed PVC pipe.
It is desirable for a column of risers and an underground septic tank or other tank-type structure to be water-tight. One reliable manner of testing the ability of these structures to retain water is to test their capacity to maintain a vacuum. Those riser components that are formed to have a tongue-and-groove connection, including a female connecting portion having a downwardly-open, i.e. inverted, generally U-shaped cylindrical channel for connecting to a lower riser component, and a male cylindrical connection at an upper end for being received in the female connection of a next-higher riser component, are found to be capable of maintaining a suitable vacuum when formed into a column. A suitable vacuum-tight interconnection between a lowermost riser component and a manhole or other access means is therefore desirable.
Instead of having to cast a lowermost riser or riser pan into a concrete lid of a concrete septic tank, it would be desirable to provide an adapter on top of a concrete lid in a manner that accepts a lower connecting portion of a riser or riser pan, in a suitably vacuum-tight manner, and which adapter can be suitably sealed to the concrete lid. It would further be desirable if that same adapter could be used in place of riser interfaces conventionally employed at the access opening of roto-molded or blow-molded plastic tanks. For instance, known roto-molded or blow-molded plastic tanks have used blow-molded plastic risers with interlocking lugs at the bottom of at least a lowermost riser, which interlocking lugs are received in complementary slots in the vicinity of the access opening of the tank. Alternatively, some blow-molded plastic tanks have been molded so as to provide a threaded portion in the vicinity of the access opening, and a complementary threaded portion on a connecting end of a riser to be received thereon. As the lowermost riser is rotated with respect to the access opening of the tank, the lugs or threads serve to lock the risers in position. However, such risers have limited versatility, as they typically can only be used with a single manufacturer's tank system. Furthermore, risers typically used with such blow-molded or roto-molded plastic tanks have not achieved an adequate water-tight, vacuum-tight seal with adjacent risers, or with the access opening of the tank. Epoxy kits offered by certain plastic tank manufacturers for use in securing a lowermost riser at the access opening of blow-molded plastic tanks have likewise not achieved a sufficient vacuum-tight seal with the lowermost riser.
It is also desirable to convert corrugated polyethylene pipe, ribbed PVC pipe, concrete risers, and other risers lacking a tongue-and groove connection, to be compatible with risers having a tongue-and-groove connection (which achieves significantly greater vacuum-tightness as opposed to other riser connections). It would also be desirable to make manholes and other access means of concrete, plastic, and fiberglass underground septic tanks and other waste structures, drainage structures, pumping stations, or lift stations to be compatible with such substantially vacuum-tight risers having a general tongue-and-groove connection. It would also be desirable to provide an adapter ring that would enable a flat surface of, for example, a concrete lid of a septic tank to accept stackable riser components without having to cast into, or drill holes into, the flat surface.
Thus, there is a need for a single form of multi-use adapter component that will efficiently convert the access opening, so as to accept a vertical stack of riser components in a substantially water-tight and substantially vacuum-tight arrangement, for any of a plurality of applications, such as (by way of example only) a concrete septic tank, a plastic (e.g., blow-molded or roto-molded) tank, a fiberglass tank, a pumping station, a lift station, a plastic riser, a concrete riser, a length of corrugated pipe, or a length of ribbed PVC pipe.